Gray Iron

Overview

Dura-Bar continuous cast gray irons contain flake graphite in matrix structures that range from all pearlite to pearlite plus ferrite depending on the grades. The flake configuration corresponds to ASTM Type VII and is available in Type D, size 6-8 or Type A, size 4-6.

The matrix structure will influence machinability, strength, hardness and wear characteristics. In general, a fully pearlitic matrix will have the best mechanical properties and will be readily machinable. Bars containing ferrite in the matrix will be easier to machine but will be lower in strength and wear resistance.

Iron Stock Grades Non-Stock Grades
Gray G2, GX, G2S, G2P G1A, G2A

The graphite structure influences strength, surface finish and hardness.The most common gray iron specification will contain Type VII flakes, type A, size 4-6, as evaluated in ASTM A247. Dura-Bar G2 gray iron will contain this type of graphite distribution and will be best suited for applications requiring moderate strength, good vibration damping and thermal conductivity, along with optimal machining characteristics. Dura-Bar G2 is built around ASTM A48 Class 40 gray iron.

Dura-Bar G2P and G2S will have the same graphite distribution with a highly pearlitic core matrix and mostly pearlitic rim matrix aiding surface hardenability. Dura-Bar G2S is alloyed with molybdenum to obtain higher tensile strengths throughout the continuous cast product and maintain strength in elevated temperature applications. Irons containing finer flake sizes are available in the G1A and G2A grades. The graphite distribution is Type VII flakes, Type D, size 6-8, as per ASTM A247. Irons containing Type D graphite are most often specified for glass and other permanent mold applications, when excellent surface finishes are required.


Gray Iron Grade Comparison

Grade Tensile Strength (psi min) Fatigue Strength (psi) Extended Sizes
G2 > 40,000* 20,000  
GX > 40,000* 20,000 Yes
G2S > 40,000* tbd  
G2P > 40,000* tbd  
G2A > 40,000* 25,000  
G1A > 25,000* 15,000  

* Gray iron tensile strengths are based on the strength of a cast test bar. For more information download our Dura-Bar ASTM A48 Policy tech brief. Gray iron will not yield/elongate before fracture. The behavior of gray iron is non-ductile.


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